Considering the high costs associated with diamonds, finding a suitable birthstone gift for the month of April can be a challenge. The trick is to look deeper into the subject of gemmology to find white and colourless gemstones that can serve as fantastic alternatives. Here, Gem-A Tutor Pat Daly shares his thoughts on this quest for more budget-conscious options…
Birthstones are gem materials associated with the different months of the year and are sometimes thought to bring good luck to those who wear them. There is, however, no universally accepted list of birthstones. Several have been used since ancient times, and they do not agree in all details. In different traditions sapphire, for example, is variously assigned to April, July, August and September.
The linking of stones with months goes back more than an estimated 3,500 years to Tibetan and Indian traditions, and it continued during classical Greek and Roman times, the medieval period and to the present day. Throughout history, scholars have tried to classify gemstones, originally by their appearance and then by their durability and density. Identification methods were limited until their chemical compositions and crystal structures were better understood in the 19th century. This means that the names given to gems in past centuries may not be the same ones we would use today, and a name might now be applied to a different stone. We cannot always be certain that we know the identity of the stones listed in ancient documents. Nor can we be sure that the months we recognize span the same parts of the year as the time periods used in the distant past.
A selection of zircon gemstones, including a colourless option (bottom left), from the Gem-A Archives.
Details of calendars have changed over time. Modern systems offer alternative stones of different values, which increases the potential for choice, and they include varieties, such as alexandrite and tanzanite, which were unknown before the 19th century.
Therefore, there are good reasons to substitute another stone for a listed one that may be too expensive or not satisfy a customer’s taste.
Diamond is commonly considered a white stone, though most of them incorporate a hint of yellow and may be of any colour. Stones that are white or nearly so are probably the best alternatives to diamonds. Those which are most often suggested are sapphire, rock crystal, topaz and opal.
Diamond is valued for a unique combination of properties. It may be completely white and perfectly transparent. Its lustre is the brightest that can be seen on non-metallic materials and has been chosen as the standard against which other stones are compared. Its high refractive index is expressed as the brilliance for which well-cut stones are famed, its property of dispersion, or fire, is the highest of all natural white gemstones which are commonly used in jewellery, and its single refraction means that there is no tendency for facet edges seen through the stone to appear blurred or out of focus.
White beryl from Brazil, photographed by Henry Mesa.
Any material may be broken, but diamond has a reputation for toughness, and it is the hardest of all gemstones. The rarity and value of diamond means that cutters can afford to spend the time to cut flat, well-polished facets at the correct angles, to produce fashioned stones which are sufficiently well proportioned and symmetrical to display its desirable optical properties, and it is durable enough to preserve the sharp edges and corners, and unscratched facets, which are needed for this purpose.
No other stone can compete with this combination, but they do supply some of these features and their lower values mean that they are available in much larger sizes than the diamonds which most people can afford.
Rough rock crystal specimen, photographed by Henry Mesa.
Topaz and the rock crystal variety of quartz are available in large, transparent, inexpensive pieces which may be faceted or, in the case of rock crystal, fashioned into table ornaments. Both are hard, though they do not compare well with diamond in this respect, and they are reasonably tough. Neither displays much fire, however, and their relatively low refractive indices mean that they cannot show brilliance at the range of viewing angles which is possible for diamond. In addition, their low value prevents lapidaries from investing the time needed to get the best optical effects from them, so the quality of polishing tends to be commonplace.
Faceted quartz with a pyrite inclusion, photographed by Henry Mesa.
White sapphires are more expensive. Good quality stones may cost hundreds of pounds per carat. The refractive index of sapphire is high enough to make a good brilliance and lustre possible on well-polished stones, but they are lacking in fire compared with diamond. Sapphire is tough and, among natural stones seen in jewellery, it is second only to diamond in hardness.
A selection of topaz gemstones, including a colourless option (top left). Photograph by Pat Daly.
White opal is not comparable to diamond in the same way as transparent white stones. It is soft, brittle and translucent, but it displays spectral iridescence, which is rare amongst gemstones. It, too, is expensive in its better qualities, and prices can be similar to white sapphire. However, white opal is a true alternative to diamond, since it does not compete with it, but offers a different kind of beauty, displaying flashes of brilliant colour against a subdued background in which brilliance and fire play no part.
In addition to the stones described above, there are about six common white stones and another six, which are rarer but not too hard to obtain in the gem trade and might be added to the list.
Since alternatives exist, there is no need to restrict the choice to one stone; a collection could be made of those which are easily available. As a point of interest, there is a collection of white gemstones, which was comprehensive at the time it was made, that was donated to Gem-A by David Kent, a well-known gemmologist, teacher and examiner for the Association.
Main image: rough diamond crystal photographed by Henry Mesa.